SingletonPtr's implementation wasn't totally safe - see "C++ and the
Perils of Double-Checked Locking"by Meyers and Alexandrescu. No problems
observed in practice, but it was potentially susceptible to compiler
optimisation (or maybe even SMP issues).
Now that we have atomic loads and stores, the function can be made safe,
avoiding any potential races for threads that don't take the lock:
ensure that the unlocked load is atomic, and that the pointer store is
atomic.
See https://preshing.com/20130930/double-checked-locking-is-fixed-in-cpp11/
for more discussion.
Like all HAL APIs, the calls in trng_api.h are not expected to
be thread-safe.
All current accesses to the TRNG HAL are currently via
`mbedtls_hardware_poll`. Mbed TLS does not currently serialise these
calls itself, as `MBEDTLS_THREADING_C` is not enabled. But even if
Mbed TLS's own accesses were serialised, there are other direct
users of `mbedtls_hardware_poll` such as randLIB, that need to use
direct calls due to lack of API to extract entropy from Mbed TLS.
As such it makes sense to treat `mbedtls_hardware_poll` as a de facto
public Mbed OS API, akin to the C++ veneers on top of the HAL, and add a
PlatformMutex there so that it is safe for multithreaded use.
Instead of doing a "pull --rebase" to update to the latest development
branch, do a "fetch" followed by a "checkout" to update to the specified
release. This enables us to get any new tags created since the last
update to the development branch, and removes the noise of updating a
local "development" branch.
As barriers were added in #9247, review comments pointed out that atomic
stores needed a second barrier, and they got one. But atomic_flag_clear
was missed.
DAPLink implementation on Cypress kits cannot handle hex files
with 64 bytes per row: refer to https://github.com/ARMmbed/DAPLink,
source/daplink/drag-n-drop/intelhex.c, hex_line_t struct, data field.
Below are the options read from the toolchains/arm
armclang --target=arm-arm-none-eabi -mcpu=list
The following arguments to option 'mcpu' can be selected:
-mcpu=cortex-m0
-mcpu=cortex-m0plus
-mcpu=cortex-m1
-mcpu=cortex-m3
-mcpu=cortex-m4
-mcpu=cortex-m7
-mcpu=cortex-m23
-mcpu=cortex-m33
...
armlink --cpu=list
The following arguments to option 'cpu' can be selected:
--cpu=Cortex-M0
--cpu=Cortex-M0plus
--cpu=Cortex-M1
--cpu=Cortex-M1.os_extension
--cpu=Cortex-M1.no_os_extension
--cpu=Cortex-M4
--cpu=Cortex-M4.no_fp
--cpu=Cortex-M7
--cpu=Cortex-M7.fp.sp
--cpu=Cortex-M7.no_fp
--cpu=Cortex-M23
--cpu=Cortex-M33
--cpu=Cortex-M33.no_fp
--cpu=Cortex-M33.no_dsp
--cpu=Cortex-M33.no_dsp.no_fp
...
armclang --target=arm-arm-none-eabi -mfpu=list
The following arguments to option 'mfpu' can be selected:
-mfpu=fpv4-sp-d16
-mfpu=fpv5-sp-d16
-mfpu=fpv5-d16
...
Kevin Bracey
Amir Cohen
Mirela Chirica
itayzafrir
Jaeden Amero
Veijo Pesonen
Martin Kojtal
Brian Daniels
Cruz Monrreal II
Volodymyr Medvid
Amanda Butler
deepikabhavnani